1. Field of the Invention. angioplasty catheters, and particularly to an adjustable manifold assembly which provides improved efficiency and accuracy in the manufacture of catheter assemblies.
2. Description of the Prior Art.
In the field of angioplasty, specially designed dilatation catheters are used for treating various types of vascular diseases. Angioplasty dilation catheters are available in a number of different sizes and shapes, depending upon the intended use. Some of them, particularly those used for opening of stenoses in the coronary arteries, are very small, and much engineering effort has gone into reducing the size and increasing the flexibility of the tip area of these catheters, while maintaining the strength thereof, to make it easier to advance the catheter through the vascular system and cross a stenosis that is to be dilated.
Various constructon techniques are used for such catheters. One common class of devices is made from an inner tubular member and a coaxial outer tubular member. The inner tubular member extends the length of the catheter and has a central or "thru" lumen designed to receive a guide wire, whereby the catheter can be advanced over a guide wire previously introduced into the patient's vascular system and steered to the site of the stenosis. The outer tubular member is positioned generally coaxially around the inner member and extends substantially the length of the catheter, defining an annular inflation lumen between the two members. An inflatable balloon member is provided at the distal end of the catheter, and is connected with the distal ends of the inner and outer tubular members such that the annular lumen communicates with the interior of the balloon and may be used for inflation and deflation thereof. At the proximal end of the catheter, both the inner and outer tubular members are received and secured in a manifold or handle assembly which is used for manipulation of the catheter and which has suitable fittings for receiving the guide wire and for connection to a controllable source of inflation pressure, as is generally known in the art.
In the manufacture of angioplasty catheters, problems have been encountered in the attachment of the inner and outer tubular members in the manifold assembly. It has been difficult to provide adequate pressure sealing, in view of the fact that the parts are made of thin walled plastic material, and in view of the fact that in use the balloons will be subjected to pressures of over 200 psi. Another problem is that errors or inaccuracies in the lengths of the tubular members or the manner in which they are secured within the manifold assembly have resulted in mismatches in lengths The inner member might be too long or too short with respect to the outer tubular member. Either condition results in a strain or distortion within the catheter, which can cause problems in the tip area thereof, since the tip including the inflatable balloon is the most flexible part of the catheter These strains or distortions can manifest themselves as certain unwanted wrinkles or bends that can interfere with the intended flexibility of the tip, and can even cause an unwanted "set" or preferred flexing direction which can cause problems in advancing the catheter to the site of a stenosis to be treated. Because the inner and outer members may have different moduli, the degree of mismatch, strain and distortion can change between the uninflated and inflated states, further complicating the use of the catheter In many cases it has been necessary to inflate the catheter at the factory for adjustment during assembly to minimize distortions of the tip area in the inflated state.
Because of these problem areas, mass production has been difficult in the prior art, and therefore the usual practice is to custom-build each catheter.